Hydrangeas (Hydrangea macrophylla)
These shrubs are widely grown in Australian gardens for their cool blue or pink flowers from summer to autumn. These deciduous shrubs can be grown as feature plants, as an informal hedge, or as a container or courtyard plant. They are well suited to that shaded part of the garden on the east or southern side of the house and are easy to grow from cuttings, which are taken in winter when plants are dormant.
Hydrangea macrophylla is known for its variable flower colour, which is a simple indicator of soil pH. Responding to the soil, hydrangeas flower blue in acid soils and pink in alkaline conditions. This variation is due to the availability of aluminium ions in the soil. The greater availability of aluminium in acid soils leads to increased blue colouration in the flowers.
There are two types of flower heads. Commonly grown are mophead varieties with large flower heads made up of a mass of small infertile flowers. Daintier and less familiar are lace-cap hydrangeas. These have a central cluster of tiny fertile flowers surrounded by a fringe of infertile flowers to give a lacy effect.
The large mophead flowers are produced on new wood, allowing flowers to be produced consistently throughout the summer season. In addition removing spent flower heads will encourage the formation of new flowers.
While hydrangeas are often sold as the species, there are many named varieties in sizes that range from under 1m to well over 2m in height and some of the newer varieties have double flowers or colourful stems. Check out your local hardware or garden centre for varieties to suit your location. Here are a few to get you thinking:
- Hydrangeas (Hydrangea macrophylla) ‘Endless Summer’ A long-flowering variety new to Australia. It has large mophead blue or prink flowers (depending on the soil’s pH) which are produced on new wood. Remove spent flowers to get vibrant blooms from summer through to autumn.
- Hydrangeas (Hydrangea macrophylla) ‘Blushing Bride’ From the same series as ‘Endless Summer’, it has stunning pure white mophead flowers that gradually fade to pale pink as the flowers mature. They make a great addition to any vase arrangement.
- Hydrangeas (Hydrangea macrophylla) ‘Obsidian’ It is known for its abundant display of beautiful large fuchsia pink large mop top and lace cap flowers with stunning long black stems. A great variety for any garden as it can withstand frost and high temperatures.
- Hydrangeas (Hydrangea macrophylla) ‘Broomstruck’ A beautiful repeat flowering hydrangea with a deep red mophead flower which can move to pink or blue depending on the pH of the soil. It will perform well given a part shade position in the garden.
- Hydrangeas (Hydrangea macrophylla) ‘Tea Time Bicolour’ A unique bicolour variety with flowers with white borders and pink or blue flowers depending on the soil’s pH. A show stopper in any garden throughout the summer and early autumn, they prefer a shady position to look their best.
- Hydrangeas (Hydrangea macrophylla) ‘Tuxedo Red’ A new stunning hydrangea for both foliage and flowers. It has striking dark purple/black, dense foliage against balls of red flowers which intensifies as the flowers mature. Planted in a shady position they will keep blooming throughout summer.
Aspect Hydrangeas need a sheltered location with shade to part shade. In cool climates hydrangeas can tolerate full sun but will need extra watering. Protect hydrangeas from strong winds as their stems can be brittle.
Soil They grow best in a rich, fertile soil that holds moisture so dig in homemade compost or organic matter and/or Seasol Super Compost to prepare for planting. Reapply organic matter in winter as plants start to grow in spring and again in autumn after flowering to revitalise the soil. If growing In a container, use a premium potting mix such as Seasol Advanced Potting Mix.
Climate Hydrangeas grow in all areas except the tropics. In hot inland areas they require shade and additional water during summer. During periods of high heat they may need to be covered with shade cloth during the day. Remember to remove it in the cool of the evening.